Neither phone is worth buying unless you have a serious discount for a one year deal.
- The iPhone isn't worth buying unless you have a mac, don't use Microsoft Word Excel and Powerpoint for work, don't really care about the ease of drag and drop for documents and media files, don't mind converting everything to the iPhone format and losing any backup should your desktop version become corrupted, and don't mind paying for numerous proprietary accessories and access for items to be determined such as the new publishing model will affect current apps. I had one once. It was an eye opener. Works for people who really want/need a very simple existence.
- The Thunderbolt is a major work in progress with a terrible battery. Verizon stores here locally have told me that they are pushing the extended battery to all Thunderbolt users because of how paltry the tiny 1400mAh one is (smaller than the EVO.) Unless you plan on waiting a while until all the other problems of this phone are fixed (the Internal memory problem) and that includes optimizing the battery so you get fair battery life from the standard battery, at best.
My advice - keep it together. Wait 2 months for the Motorola Bionic to come out. As much as I love HTC Sense and think that they do many things well, they really wrote their own marketing death with the Thunderbolt and making a smaller battery than the EVO. Perhaps it was Verizon Wireless' idea. Whomever it was, you don't have to deal with these issues if you're patient. I got mine because of a sparkling great deal on a 1 year plan and the question of tiered 4G pricing.
My guess - after the poor Thunderbolt launch, 4G prices will stay stagnant for the launch of the next 4G phone. They need to in order to restore some type of confidence in the next 4G phone.